(1) Field of the Invention
This invention relates to multilayer metallurgy semiconductor packages, and more particularly to multilayer ceramic packages adapted to interconnect a plurality of large scale integrated circuit chips.
(2) Description of the Prior Art
The advent of large scale integrated circuit (LSI) semiconductor devices has produced a great increase in circuit density. To accommodate such high density LSI devices, the interconnection density of the packaging substrate must also increase. This means that the grid size which is the minimum via spacing must shrink. Grid size minima are a function of the particular material used as the interconnection support. The high performance LSI's require grid sizes about one-tenth that presently achievable by multilayer ceramic (MLC) technology. Dimensions on the interconnection substrate must approach those of the LSI chips.
An attempt has been made to apply the metallization technology in the manufacture of semiconductor devices, to the fabrication of packaging substrates, in particular to making connections between the relatively large metallurgy of the MLC substrate to the input-output (I/O) terminals of the device by providing additional top transistion layers on the MLC substrate. However, there are large differences between a packaging substrate and its function and that of the LSI chip. Because of longer signal lines on the packaging substrate, conductivity of the lines must be higher. They requires larger dimensions and as a consequence, a thicker dielectric and finally, a new layer to layer via technique.
Innumerable different thin film processing schemes for high-density interconnections have been developed, and others are still being explored to satisfy the demands of performance reliability, and cost.
Examples of packages that include an MLC or glass ceramic substrate provided with an interconnection layer system to establish electrical contact between the circuitry in the substrate and the device I/O's are shown in U.S. Pat. No. 4,430,365 and U.S. Pat. No. 4,665,468.